Can anyone "ever" be prepared for "all" situations? No, however...
Hindsight being 20/20 and at the same time trying to learn from others...On any long trip (especially during this time of year and in the environment they were in) - I would suggest having a GPS, some sort of signaling devices (mirror, flares, smoke, air horn, whistle - all fit in a small space) and of course additional applicable gear depending on time of year and length of trip.
I remember driving up & down the Alaska/Canadian Highway (Alcan) with my family on orders several times. The military required we have specific gear with us, inspected that gear, and insured we had it before taking the trip. I realize of course not everyone is exposed to "the military way of doing things". (BTW, that gear included an extra spare tire, fan belts, & extra gas as well.)
IMHO, one valuable tool related to our "Flashaholic" hobby is one of the
Laser Rescue Lights/Flares produced by Greatland Lasers here in Alaska.
They aren't just for hikers, hunters, fisherman, mariners...anyone traveling should have one!
They're a pretty big selling item up here - easy to feed & carry. I'm not saying it would have helped this family though. Too many situational events per specific incident could affect the success of any method.